Current practice is to treat patients with medication, and only when drugs can't control seizures -- often many years later -- does a patient become a candidate for surgery. This study suggests that some patients with focal epilepsy -- the most common form of the seizure disorder -- should be eligible for surgery sooner, the British researchers said.

"Neurosurgical treatment of focal epilepsy that does not respond to medication can result in remission of seizures, with 82% of individuals having great benefit and [many] never having another seizure," said lead researcher Dr. John Duncan, a professor of neurology at the National Hospital for Neurology and Neurosurgery and Imperial College London in England.

Based on these results, "Epilepsy surgery should be considered if two to three medications have failed to control seizures," he said.

Given the severity of some epilepsy-drug side effects (they are thought to increase the risk of birth defects when taken in pregnancy), certain patients might welcome a surgical alternative, the researchers said.

For the study, published in the Oct. 15 issue of The Lancet, Duncan's team looked at the long-term outcome of 615 adults who underwent epilepsy surgery at the National Hospital between 1990 and 2008. On average, the patients had suffered seizures for 20 years prior to surgery.

Five years post-surgery, 52% of the patients remained seizure-free, and after 10 years, 47% were free of seizures, the researchers found. However, over the long-term, 11% had what are called simple partial seizures, which do not involve loss of consciousness but appeared to affect their odds of recovery.

Surgery for epilepsy involves cutting away a small part of the brain where seizures start. Most often this is an area of the temporal lobe, and this procedure is known as an anterior temporal resection. But depending on the location of the "seizure focus," which doctors determine with MRI and other tests, epilepsy surgery may be performed on other areas of the brain.

Surgery outside the temporal lobe is called extratemporal cortical resection. The researchers found that patients who underwent extratemporal resections were twice as likely to have seizures return as those who had a temporal resection.

In addition, patients who had simple partial seizures in the two years after surgery were 2.5 times more likely than others to have seizures that did affect consciousness.

Also, the longer patients remained free of seizures, the less likely they were to relapse. But remission was less likely the longer seizures persisted, the authors noted.

In some patients, use of a previously untried antiepileptic drug was linked to fewer seizures after surgery, but the study wasn't designed to evaluate medications.

Most patients chose to continue taking epilepsy drugs after surgery, but at the end of the follow-up period, 28% of those who were seizure-free stopped taking them altogether.

No patients saw a significant worsening of their epilepsy after surgery, the researchers noted.

In the first year post-surgery, 82% were seizure-free or only had simple partial seizures, but that didn't indicate a cure.

Dr. Joseph I. Sirven, professor and chairman of the department of neurology at the Mayo Clinic in Arizona and chair-elect of the Professional Advisory Board at the Epilepsy Foundation, explained the significance of the research, saying "this is one of the largest series of epilepsy surgery patients which included both temporal and extratemporal lobe resection for drug-resistant epilepsy."

The study underscores that epilepsy surgery works with almost 50% of patients with no worsening of the epilepsy after surgery, he said.

"The trial is important because it once again highlights the safety and effectiveness of surgical therapy in a real world clinical environment," Sirven said.

The study authors said doctors now need to improve the process for selecting potential candidates for surgery.